Of Irish descent, Prosper Odend'hal came from Saint-Cyr in 1887 and arrived in Tonkin two years later. He then undertook missions throughout the Annam chain: 1890, discovery of the pass of Lao Ai with one of the officers attached to the Mission Pavie, 1892, mission in the region of topographic Phan Rang, 1893, seeking a way to easy communication between Quang Nam and the river Attopeu. In 1894, he was chosen by the Governor General to lay the foundations of the organization of Laos. He established his position in Savannakhet, the medium Mekong, across from the gap of Ai Lao. It administers the province of Savannakhet and Attopeu until 1897. He was appointed to Phan Rang, where he remained resident until 1902.
He then cooperated with the EFEO to inventory antiques from Phan Rang and received the title of correspondent in March 1903. For a mission to explore archaeological, philological and ethnographic Laos, it needs to be seconded to the EFEO. His project accepted, part of Phan Rang in February 1904 to win the Darlac Laos. He stops in countries Jarai, whose tribes have Sadetes chiefs, kings of Water and Fire, he wants to ally with France. As of April 7, Odend'hal is in the hamlet of Palei Koueng (north of Ban Me Thuot), ready to go give this a buffalo Sadete Water, promised in exchange for a peace agreement signed with France. It's going to carry on now that he was killed. A monument is erected to his memory at Phan Rang in 1909.